The first clinical trial to treat people suffering from severe spinal cord injury with human embryonic stem cell therapy received the go-ahead from the U.S. Food and Drug Administration on Friday, after a clinical hold was placed for almost a year due to safety concerns.

The hold was placed just several months after the FDA first approved the trial in January, 2009 following results from a single preclinical animal trial which found that animals developed small cysts within the injury site in the spinal cord. The prevalence of cysts was higher in this trial than previous studies, the company said. Geron developed new markers and assays, or blood tests, and completed another preclinical animal study before submitting a request to the FDA to lift the hold.

The Phase I clinical trial will test the drug's (GRNOPC1) safety in human patients. The drug contains hESC-derived oligodendrocyte progenitor cells that have shown remyelinating and nerve growth stimulating properties, leading to restored function in lab animals with acute spinal cord injury.
The company's therapy uses various growth factors to turn embryonic stem cells into precursors of the neural support cells (oligodendrocytes). These are then injected into the spinal cord at the injury site. If the therapy works, the injected cells will help repair the insulation around the nerve cells, which could restore the ability of some nerve cells to carry signals. And it's possible that the growth factors produced by the injected cells could help damaged nerve cells to regenerate.

"Our goals for the application of GRNOPC1 in sub-acute spinal cord injury are unchanged -- to achieve restoration of spinal cord function by the injection of hESC-derived oligodendrocyte progenitor cells directly into the lesion site of the patient's injured spinal cord," said Dr. Thomas Okarma, the company's president and CEO, in prepared remarks.

The company is also looking into using the therapy in other illnesses, including Alzheimer's, multiple sclerosis and Canavan disease, Okarma said.

The clinical trial sites have not been made public. Geron (GERN) stock was up 17% on the news Friday. Another company, Advanced Cell Technology, is also working on stem cell research.

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